Probability sampling ensures every individual in a population has a known, non-zero chance of being selected, providing a representative sample for statistical analysis.

Option A (Random sampling): This is the correct answer. Random sampling, where each patient has an equal chance of selection (e.g., using a random number generator), is a probability sampling method. NAHQ CPHQ study materials highlight random sampling as a rigorous approach for surveys to ensure unbiased results.

Option B (Convenience sampling): Convenience sampling (e.g., surveying available patients) is non-probability sampling, as it does not ensure representativeness and is prone to bias.

Option C (Focus group sampling): Focus group sampling is typically purposive (non-probability), selecting participants based on specific criteria, not random chance.

Option D (Quota sampling): Quota sampling is non-probability, as it involves selecting a fixed number of participants from predefined groups, not ensuring equal selection probability.